The present invention generally relates to computer memory systems, and more particularly to a modular mass storage system that enables storage devices to be installed and removed from a computer without the use of cables through which the storage devices receive power and exchange data with the motherboard of a computer system.
Current data (mass) storage devices in personal computers (PCs) and servers typically use rotatable media-based hard disk drives (HDDs) featuring one or more magnetic platters as the data carrier and a read/write head positioned over the relevant sector by means of an actuator. In recent years, the trend has been to miniaturize these HDDs such that currently the largest form factor is the 3.5-inch drive. The 3.5-inch HDDs are still the predominant non-volatile storage device in desktop computers, where they are typically mounted in drive bays. In the notebook sector, the more common HDD is the 2.5-inch drives in a slim form factor mounted in a specialized compartment in the notebook chassis.
Aside from physical dimensions, the weight of an HDD plays an important factor with respect to the mounting of an HDD in a computer, since certain prerequisites must be met for the mounting fixture. Moreover there are also some orientational factors that must be taken into consideration, for example, drives mounted at an angle appear to have higher wear on their bearings than do drives oriented so that their spindle axes are vertical during normal operation of the computer. Finally and significantly, the mass of the actuator is often sufficient to cause some degree of movement of the entire drive. Primarily because of these weight and stability concerns, HDDs are often mounted in specialized drive bays within the chassis, often with the use of rubber grommets to dampen vibrations and shock between the HDDs and the chassis. Power and data connections are made through cables to the motherboard or any add-on host-bus controller, as well as the power supply unit (PSU) of the computer.
The introduction of solid state drives (SSDs) into the computer market has lessened and in some cases eliminated some of the above-noted concerns associated with HDDs. SSDs are slimmer, lighter and lack moving parts, and therefore their operation is intrinsically vibration-free and they have almost unlimited shock resistance. Likewise, SSDs are not sensitive to orientation whatsoever. As such, SSDs allow for a wide spectrum of mounting methods for computer systems.
Redundant arrays of independent disks (RAID), which encompass computer data storage schemes that divide and replicate data among multiple HDDs, utilize a dedicated controller, such as an ISA (industry standard architecture) bus or a PCI (peripheral component interconnect) or PCI express (PCIe) expansion card. Since the introduction of Serial ATA (advanced technology attachment), or SATA, several chipset manufacturers have added RAID functionality to their I/O controllers and Southbridges (also known as I/O controller hub (ICH) or a platform controller hub (PCH)). These RAID controllers provide a software-based RAID logic, which is sufficient for RAID Levels 0 and 1 (striping and mirroring, respectively) or a software-based RAID Level 5 configuration with distributed parity in which the central processing unit (CPU) handles the parity calculations. In either case, several HBA (host bus adapter) interfaces or channels are using a unified upstream signal path to the system memory for direct memory access (DMA), in which the HBA acts as bus master to initiate the data transfers.
In another approach, Fusion-io recently introduced a PCIe-based RAID card with onboard, fully-integrated multiple arrays of NAND chips. Advantages of this approach are that the PCIe interface provides a large amount of bandwidth to the system logic, and the NAND chips are not interfaced through additional cabling and logic but instead are addressed directly through an integrated controller on the card. Despite its technical elegance, there are certain concerns regarding this technology in its current form. Regarding its implementation, because the device is fully integrated instead of modular, any component failure will render the entire device inoperable. From a consumer viewpoint, because the device is at present a single-source solution, any major acceptance in the market is handicapped by a supply monopoly, and pricing may be prohibitive for wide distribution.
In view of the above, it would be desirable if further solutions were available that are capable of combining the possibilities of new generations of drives with a modular design in which off-the-shelf components can be used in any combination desired by the owner, providing a level of expandability, flexibility and serviceability at the lowest total cost of ownership.